Ch-chs



United States Patent O BIHYDROQUINONE ANTISTAIN AGENTS Anthony Loria,Paul W. Vitturn, and Arnold Wcissberger,

Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y.,a corporation of New Jersey No Drawing. Application June 3, 1953, SerialNo. 359,423

7 Claims. (Cl. 95-6) This invention relates to color photography andparticularly to a method for preventing the formation of color fog orstain in photographic emulsions.

The method of color photography in which color-forming or couplercompounds combine with the development product of aromatic aminophotographic developers to produce dyes is well known. The color formersor couplers may be added directly to the emulsion layers or may beincorporated in the developing solution as described in Fischer U. S.Patent No. 1,102,028, granted June 30, 1914, or they may be incorporatedin a waterpermeable medium which is insoluble in the carrier for thesensitive silver salt as described in Mannes and Godowsky U. S. Patent2,304,940, December 15, 1942, and Jelley and Vittum U. S. Patent2,322,027, granted June 15, 1943.

A difliculty frequently encountered in these processes is the formationof color fog or stain. When the exposed material is developed in acolor-forming developer, dye fog is frequently formed in the emulsionlayer. This is because the developing agent has been oxidized to someextent by the action of the air and the oxidized developer tends tocouple with the color-forming compound at places in the photographicmaterial where no silver image is produced. It is well known that inthese processes the dye should beformed only where the silver halide isreduced to metallic silver, thereby oxidizing the developing agent to aform which couples with the color former. Once the developing agent isoxidized, it couples immediately with the color former whether aphotographic image is present or not. Aerial oxidation of the developeror oxidation by means other than the photographic image thereforeconverts the developer to a form which will immediately react with thecolor former to produce a color fog on stain. This effect is especiallynoticeable in materials having couplers incorporated in the sensitivelayer since there is no coupler in the developing solution to react withany developing agent which is oxidized by the action of the air. Fog orstain arising from these causes is not readily controlled by the sameprocedures used to control silver fog.

The control of color fog or stain by incorporating, hydroquinone orcertain of its derivatives in photographic emulsions is described inVittum and Wilder U. S. Patent 2,360,290, granted October 10, 1944.Hydroquinones described therein include diamyl hydroquinone and dioctylhydroquinone. The dialkyl hydroquinones available at that time were thedi-secondary and di-tertiary hydroquinones such as 2,5-di-tertiary octylhydroquinone. This compound has good stain preventing propertieswhenincorporated in photographic color films but it suffers from thedisadvantage when used in silver halide emulsion layers of causinginstability of the color developed dye to heat or light.

It is therefore an object of the present invention to provide antistainagents which cause lessinstability of the color developed dve image toheat and light. A further object is to provide antistain agents whichare easily compatible with and non-difiusing in the colloid of thephotographic layer in which they are incorporated. A further object isto provide antistain agents which are non-diffusing in the photographiclayer and which are strong enough reducing agents to react rapidly withoxidized color de- 5 veloper. A further object is to provide antistainagents which do not form highly colored oxidation products when thematerial containing them is put through an oxidizing bath. Other objectswill appear from the following description of our invention.

These objects are accomplished by the use in an emulsion layer or otherlayer of a photographic material especially a silver halide emulsionlayer in which a colored image is formed by development in a colorforming developer, of a bihydroquinone having the formula OR OR Thefollowing compounds are illustrative of those which We may use:

1. 7 OH OH Blhydroquinone on on me. 04m

on. on;

'2,2-methylene bis(5-tert.butyl-4-methoxyphenoll OH OH at r 018E"2,2'-methylene bis-5-n-octadecyl hydroquinone 4. 0 CH: 0 CH:

i Ha'lC 1 CisHn CH3 on,

1,1'-methy1ene bis(2,5-dimethoxy-4-octadecyl benzene) OH l2,2-isobutylidene bis- (4) -meth0xypheno1) Ha C 4 I C 411 C H3 8) C H3 0C H 2,2-isobutylidene bis-(-tert.butyll-methoxyphenol) 7. OH 0H 1 OH O Hp-p'-Biphenylene-bis- (aminomethyl hydroquinone) The preparation of thecompounds of our invention will now be described:

1. This compound was prepared as described by Hale and Robertson in theAm. Chem. 1., 36, 693 (1908).

2. A mixture of 180 g. (1 mole) of 3-tert-butyl-4- methoxyphenol, 300ml. of benzene, 20 g. of calcium chloride, 20.8 g. (.25 mole) of 36%formalin, 3 ml. of concentrated hydrochloric acid, and 5 drops ofthioglycollic acid was stirred at room temperature for several hours;then heated at reflux for one hour. Water was added and the organiclayer was washed free of acid. The solvent was removed and the residuedistilled in a high vacuum. The fraction boiling at 212-215 C/ 0.4-0.6mm. was collected and crystallized, first from hexane, then three timesfrom aqueous acetic acid. The product melted at 174.5-177.5 C.

3. This compound was prepared by demethylating 1,1- methylenebis(2,5-dimethoxy-4-octadecylbenzene) with AlC13 in boiling dry benzene.Aluminum chloride 20 g. (fine powder) g. of the dimethoxy intermediate,and 200 ml. of dry benzene were refluxed on a steam bath with eflectivemechanical stirring for 20 hours. The cooled reaction mixture was pouredinto 1500 ml. of cold methyl alcohol, and the solid obtained wascrystallized twice from ethyl acetate, using carbon decolorizing thefirst time. There was obtained 5.5 g. of colorless material (going pinkon standing), having a melting point of 190-191 C.

4. This compound was prepared by the method of Jacini and Bacchetti asdescribed in Gazz. 80, 760-761 (1950). Crystallized fromtetrahydrofurfuryl alcohol the product is a colorless solid melting at88-89 C.

The 2,5-dimethoxy octadecylbenzene intermediate for the abovepreparation is described by Cook, Heilbron, and Lewis in the J. Chem.Soc., 659-661 (1942).

5. This compound was prepared by the method given for 2,2-isobutylidenebis(5-tert-butyl-4-methoxyphenol) substituting 4-rnethoxyphenol for2-tert-butyl-4-methoxyphenol.

6. This compound was prepared by the method given for 2,2-methylenebis(5-tert-butyl-4-methoxyphenol), substituting isobutyraldehyde forformaldehyde. The product is a white crystal line material melting at181.5- 183.5 C.

7. A mixture of 13.8 g. gentisaldehyde and 9.2 g. benzidine wererefluxed in 300 ml. of n-butanol for 15 minutes. On cooling an orangeprecipitate formed. The precipitate was filtered, washed first with 50ml. of butanol and then with 250 ml. of ethanol. Yield: 16 g. Thematerial gets brown at about 200 C. and does not melt up to 260 C.

The 4,4'-bis(2,5-dihydroxybenzalamino)diphenyl prepared above wasreduced in dioxane solution, using Raney nickel as a catalyst and 40-50pounds of hydrogen pressure at 60-65 C. The catalyst was removed fromthe hot solution by filtration and the solution cooled. The productformed was filtered, washed with a small volume of fresh dioxane, andcrystallized twice from the same solvent. The(2,5-dihydroxybenzyl)benzidine was obtained almost colorless but turnedlight brown in the open air. It melts at 198-200 C.

The antistain agents of our invention are useful, in general, withemulsions containing couplers incorporated in the manner described inMannes and Godowsky U. S. Patent 2,304,940 or Jelley and Vittum U. S.Patent 2,322,027.

Couplers such as those described in Weissberger U. S. Patent 2,298,443and Salminen and Weissberger U. S. Patent 2,423,730, when incorporatedin this way, produce dyes upon color development which are prone tofading by the action of visible or ultraviolet light, when knownantistain agents such as 2,5-di-tert. octyl hydroquinone are used in theemulsion layer. These are the yellow and cyan dyes. The magenta dyes,such as those formed from couplers described in Loria, Weissberger andVittum U. S. Patent 2,600,788 are relatively little affected by theknown antistain agents upon the action of light.

In order to illustrate the eflect of our antistain agents, the followingtest was made.

A quantity of the antistain agent the molar equivalent of 0.05 g. of2,5-di-tert. octyl hydroquinone, was dissolved with 0.5 g. of coupler in1.5 cc. of dibutylphthalate. To this solution was added 11 cc. of 10%gelatin solution and 2.8 cc. of 5% alkanol B (sodium alkyl napthalenesulfonate) solution. The resulting mixture was passed through a colloidmill three times, and to the resulting dispersion, 32 cc. of agelatino-silver halide emulsion were added, and the mixture blended andcoated on a film support so that the antistain agent was equivalent to 5mg. per square foot of 2,5-di-tert. octyl hydroquinone.

Two check coatings were made: One containing no antistain agent, and onecontaining 5 mg. per square foot of 2,5-di-tert. octyl hydroquinone.

The film strips were exposed on a Ib sensitorneter using a silver wedgevarying in density from 0 to 3. They were then developed 10 minutes at68 F. in the following developer:

G. 2-amiuo-5-diethylamino toluene HCl 2 Sodium sulfite (desiccated) 2Sodium carbonate, monohydrate 20 Potassium bromide 2 Water to 1 literThis was followed by 5 min. in the following stop bath:

Sodium sulfite, desiccated g Acetic acid (28%) cc 235 Boric acid,crystals g 37.5 Potassium alum g 37.5

Water to 1 liter After washing, bleaching in ferricyanide-bromide,fixing in 30% hypo solution and again washing, the wavelength-densitycurves for each coating were read before and after exposure to visibleand ultraviolet light. The loss of density at the maximum of thewavelength-density curve after exposure in the Fade-O-Meter for 6 hoursand comparison with the check coatings under similar conditionsindicated the effect of the agent under test. The following table showsthese results:

Loss in density at maximum absorption Agent Cyan Dye Yellow Dye Check(none) 0 0 2,5-di-tert. octyl hydroquinone 21 13 Compound 1 .02 01 Cmpound 2. .04 .01 Compound 3. 01 02 Compound 4. 0 01 Compound 5 0 02Compound 6 02 03 Compound 7 0 07 These results show that all of theagents cause less fading of the cyan and yellow dyes than that caused by2,5-di-tert. octyl hydroquinone. Compounds 4, and 7 caused no morefading of the cyan dye than the check coating without antistain agent,and compounds 1, 6 and 7 caused even less fading of the yellow dye thanthe check coating free of antistain agent, that is, these cornpoundscaused some increase in density of yellow dye as well as improvingantistain properties.

Another compound useful as an anti-stain agent in photographic emulsionsis 2-p-cyanophenyl-2-imidazoline.

The antistain agents of our invention may also he used in non-sensitiveovercoating or filter layers, such as a colloidal silver interlayer ofmultilayer photographic material. In general, the antistain agents ofour invention are used in the emulsion or other layer in quantitiesranging from 0.07 gram to 4.3 grams per liter of emulsion or gelatinsolution. These values are, however, merely illustrative.

In certain cases the antistain agents of our invention may beincorporated in a processing solution such as a prebath, first developerbath, or color-forming developer used with color film which is developedwith a primary aromatic amino developing agent.

Our materials are particularly useful with color-forming emulsionscoated on paper supports where it is espe cially important to reduce theminimum or fog densities. This applies both to negative developed paperand to reversal paper as well as to transparency materials.

It will be understood that the examples and modifications describedherein are illustrative only and that our invention is to be taken aslimited 'only by the scope of the appended claims.

We claim:

1. A color-forming photographic emulsion having reduced foggingtendency, comprising a silver halide emulsion having incorporatedtherein a non-diffusing coupler compound capable of coupling with theoxidation product of a primary aromatic amino developing agent and as anantistain agent a bihydroquinone having the formula (BR OR where R isselected from the class consisting of hydrogen and a methyl radical, Ris selected from the class consisting of hydrogen and a methyl radical,X is selected from the class consisting of hydrogen and amino group andan alkyl group having from 1 to 18 carbon atoms, and Z is selected fromthe class consisting of methylene, isobutylene andN,N'-dimethylenebenzidine groups and a single chemical bond.

2. A color-forming photographic emulsion having reduced foggingtendency, comprising a silver halide emulsion having incorporatedtherein a non-difiusing coupler compound capable of coupling with theoxidation prodduct of a primary aromatic amino developing agent and asan antistain agent a bihydroquinone having the formula (I)H OH OH OH inwhich R is an alkyl group of from 1 to 18 carbon atoms.

3. A color-forming photographic emulsion having reduced foggingtendency, comprising a silver halide emulsion having incorporatedtherein a non-diffusing coupler compound capable of coupling with theoxidation product of a primary aromatic amino developing agent and as anantistain agent a bihydroquinone having the formula CH; OCH:

in which R is an alkyl group of from 1 to 18 carbon atoms.

4. A color-forming photographic emulsion having reduced foggingtendency, comprising a silver halide emulsion having incorporatedtherein a non-diffusing coupler compound capable of coupling with theoxidation product of a primary aromatic amino developing agent and as anantistain agent a bihydroquinone.

5. A color-forming photographic emulsion having reduced foggingtendency, comprising a silver halide emulsion having incorporatedtherein a non-diffusing coupler compound capable of coupling with theoxidation product of a primary aromatic amino developing agent and as anantistain agent 2,2-methylene bis(5-tert. butyl-4-methoxyphenol.

6. A color-forming photographic emulsion having reduced foggingtendency, comprising a. silver halide emulsion having incorporatedtherein a non-ditfusing coupler compound capable of coupling with theoxidation prodnot of a primary aromatic amino developing agent and as anantistain agent 2,2-methylene bis-S-n-octyl hydroqumone.

7. A color-forming photographic emulsion having reduced foggingtendency, comprising a silver halide emulsion having incorporatedtherein a non-diffusing coupler compound capable of coupling with theoxidation product of a primary aromatic amino developing agent and as anantistain agent 1,1'-methylene bis(2,S-dimethoxy-4- octadecylbenzene).

References Cited in the file of this patent UNITED STATES PATENTS

1. A COLOR-FORMING PHOTOGRAPHIC EMULSION HAVING REDUCED FOGGINGTENDENCY, COMPRISING A SILVER HALIDE EMULSION HAVING INCORPORATEDTHEREIN A NON-DIFFUSING COUPLER COMPOUND CAPABLE OF COUPLING WITH THEOXIDATION PRODUCT OF A PRIMARY AROMATIC AMINO DEVELOPING AGENT AND AS ANANTISTAIN AGENT A BIHYDROQUINONE HAVING THE FORMULA